Abstract: A zoom lens system has, from the object side, a first lens unit having a optical power, a second lens unit having a negative optical power a third lens unit having a positive optical power, and a succeeding lens unit. The first and the third lens units monotonically move toward the object side during zooming from the shortest focal length condition to the longest focal length condition. A number of predetermined conditions are disclosed which can be satisfied to ensure a high quality, compact zoom lens for a digital camera.

Abstract: A zoom lens system has, from the object side, a first lens unit having a positive optical power, a second lens unit having a positive optical power and provided at the image side of the first lens unit with a first variable air space between the first and second lens units, and a third lens unit having a negative optical power and provided at the image side of the second lens unit with a second variable air space between the second and third lens units, wherein a zooming operation is performed by varying the first and second air spaces, and wherein the zooming fulfills the predetermined condition with respect to a lateral magnification of the third lens unit in a shortest focal length condition.

Abstract: A zoom lens system has four or five lens units with the optical powers being +/-/+/- or +/-/+/+/-, respectively, from the object side. The image side lens unit has a negative optical power and is movable, along with at least one other lens unit, in a zooming operation. The zoom lens system satisfies the following conditions: 0.6<LBw/fw<1.7 and 0.6<.vertline.fN/fw.vertline.<1.7, where LBw represents a back focus length at the shortest focal length condition; fw represents a focal length of the zoom lens system at the shortest focal length condition; and fN represents a focal length of the image side lens unit. The lens system can be employed with a solid state imaging device, and an optical low-pass filter and an infrared blocking filter can be positioned between the lens system and the imaging unit.

Abstract: A zoom lens system has at least three lens units of, from the most object side, a first lens unit having a negative optical power, a second lens unit having a positive optical power and a third lens unit, wherein the distances between the lens units are varied by moving all of the lens units during zooming. The zoom lens system satisfies the predetermined mathematical condition.